A battery cell has been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. One type of battery cell is known as the lithium-ion battery. The lithium-ion battery is rechargeable and can be formed into a wide variety of shapes and sizes so as to efficiently fill available space in electric vehicles. A plurality of individual lithium-ion battery cells can be provided in a battery cell module to provide an amount of power sufficient to operate electric vehicles. Typically, in order to provide a high power density in an efficient package, a large number of battery cells (often much greater than 10) are packaged within an individual battery cell module.
Lithium-ion batteries are known to generate heat during operation and as a result of a charge cycle when recharging. When overheated or otherwise exposed to high-temperature environments, undesirable effects can impact the operation of lithium-ion batteries. Active cooling systems are typically employed with lithium-ion battery packs to militate against the undesirable overheating conditions. The active cooling systems typically involve flow channels or ribs on a cooling fin interposed between adjacent battery cells, both of which lead to non-uniform pressure applied to the external surfaces of individual battery cells. Further, the active cooling system undesirably increases the complexity of battery packs and the installation thereof by increasing the required packaging space and decreasing a volumetric efficiency. Additionally, significant temperature variations still may occur between individual battery cells within the same battery pack due to uneven cooling, further impacting the battery cell module operation.
Moreover, as lithium-ion battery cells charge and are discharged, they may expand, and they may expel gases as a byproduct of the chemical reaction occurring therein. It is desirable to contain the expansion of the cells, and the resultant internal pressures generated within a battery cell module due to the expansion of battery cells. It is further desirable to contain the by-product gases, and to either capture or properly exhaust the gases from the battery cell module.
There is a continuing need for an easily manufacturable battery cell module having an integral cooling system and method for maintaining a desired temperature and power density of a battery pack such as a lithium-ion battery pack. Desirably, the battery cell module and method provides a uniformly distributed surface pressure to the battery pack, while maintaining effective heat transfer therefrom and allowing the containment or capture of any expelled gases generated within the cell.